A fiber reinforced resin molded object comprising reinforcing fibers such as carbon fiber, glass fiber or aramid fiber and a resin is, since it is light and has a high durability, used as various structural members, such as, of car and aircraft.
As methods for molding the fiber reinforced resin molded object, for example, an autoclave molding method in which a laminate made by laminating prepreg sheets, which are reinforcing fiber sheets impregnated with a resin, are pressed and heated in an autoclave to cure the resin is generally employed.
However, in the autoclave molding method in which the prepreg sheet is used, there has been a problem that a complicated three-dimensionally shaped molded object is difficult to be molded. And, since materials cost is too high and molding time is too long, there has been a problem that production cost of the molded object becomes high. For that reason, it is the present condition that application and use of the molded object made by the autoclave molding method in which the prepreg sheet is used has not been widespread.
On the other hand, as a molding method of fiber reinforced resin molded object for solving the above-mentioned problem of the autoclave molding method, there is a resin transfer molding method (RTM method) in which a matrix resin is injected and impregnated to spaces in reinforcing fiber base (dry reinforcing fiber base) to which no matrix resin is deposited. In this resin transfer molding method, there is also a vacuum resin transfer molding method (vacuum RTM method) in which, at injection of the matrix resin, atmosphere is maintained vacuum.
In the resin transfer molding method, in general, a laminate made by laminating plural dry reinforcing fiber cloths is arranged in a mold, and by injecting a low viscosity liquid matrix resin to the laminate to impregnate the laminate with the matrix resin, and after that, by heating it by an oven or the like to cure the matrix resin, a fiber reinforced resin molded object (so-called composite material) is molded.
In this way, in the resin transfer molding method, since a dry reinforcing fiber base is used, it becomes possible to shape the reinforcing fiber base along a complicated three-dimensional shape. However, by only simply placing a necessary number of the reinforcing fiber cloths in the mold by laying on the other in turn, it is difficult to produce a composite material in which reinforcing fiber cloth has no significant wrinkles and the reinforcing fibers distribute nearly uniformly, and in addition, having a high fiber volume fraction Vf (volume percentage occupied by reinforcing fiber in total volume of molded object).
As a method for solving this problem, a method employing a preform in which a laminate made by laminating plural dry reinforcing fiber cloths is, in consideration of shape of molded object to be molded, preshaped according to the shape, is prepared and molded into a molded object by using it. However, this work for preparing the preform and quality of the preform bring about a great influence to production cost and quality of the composite material.
Furthermore, in order to inject and impregnate the matrix resin into the preform, it is necessary to arrange resin diffusion media (generally, referred to as media material) on a surface of the preform to diffuse the matrix resin, and in addition, in order to prevent an integration of the media material to a molded article, it is necessary to arrange a release material (release sheet) between the preform and the media material.
However, since the release material is, generally, a cloth such as of polyamide or polyester fiber, and media material is, generally, a net-like material (mesh) formed by such as polyamide, by only simply placing these materials at a desired position on a surface of the preform, these are difficult to be fixed at the position. For that reason, at arranging the preform in the mold, some fixing means, in most cases, fixing work by hand of these materials to a surface of the preform inserted in the mold by using an adhesive tape, has been considered to be necessary.
In particular, in order to arrange and fix the release material to a surface of the preform of complicated shape having a bent portion or branch portion in cross-sectional shape, there has been a problem that considerable work is required, and cost merit of the resin transfer molding method is counteracted.
After the molding of fiber reinforced resin molded object in the mold is completed, it is necessary to peel off the release material deposited to the surface of the molded object from the surface of molded object. For that purpose, in most cases, the release material is formed with a material of which thickness is small, not having good adhesive properties, and in addition, which is slippery. In a release material constituted with such a material, it becomes still more difficult to arrange it to a surface of a preform, and for arranging work, carefulness and delicate sensitivity are demanded.
In addition, since the release material is, as the above-mentioned, generally, a woven fabric such as of polyamide or polyester fiber, is poor in stretchability, there was a problem that, unless it is tightly arranged along the shape of preform, when the mold is pushed against the preform, a wrinkle is generated in the release material or a tension of the release material at position of bent portion of the preform is generated, and the mold cannot be pushed against a predetermined position, and the matrix resin is collected in the gap generated between the release material and the preform to form a resin rich portion, and quality of resin molded object formed is deteriorated.
Among these problems, apparatus for continuously producing preform for molding fiber-reinforced resin beam in which reduction of work at preform preparation step is aimed, is proposed (refer to Patent Literature 1). This apparatus for continuously producing preform is an apparatus in which, in a step of conveying two sheet-like continuous reinforcing fiber cloths, they are bent such that the respective cross-sectional shapes are U-shaped, and in addition, in back-to-back configuration, respective bottoms of the U-shape are laminated and bonded with each other, to continuously produce a preform.
However, the apparatus of this proposal is an apparatus only to produce a preform by arranging a reinforcing fiber base into a preform shape. Accordingly, this proposal teaches nothing about an idea relating to production cost from storing this preform into a mold and up to impregnating the stored preform with a matrix resin to mold a composite material, and to an arrangement of release material which affects greatly to quality of the produced composite material. This proposal cannot be said to be sufficient for a requirement to produce a low cost and high quality composite material which is ultimately desired.
Patent Literature 1: JP-2005-324513A